Metal-containing compounds

ABSTRACT

The invention relates to a novel solid state process for the preparation of metal-containing compounds comprising the steps i) forming a reaction mixture comprising one or more metal-containing precursor compounds and optionally one or more non-metal-containing reactants, and ii) using one or more hypophosphite-containing materials as a reducing agent; wherein one or more of the hypophosphite-containing materials is used as an agent to reduce one or more of the metal-containing precursor compounds; and further wherein the process is performed in the absence of an oxidizing atmosphere. Materials made by such a process are useful, for example, as electrode materials in alkali metal-ion battery applications.

FIELD OF THE INVENTION

The present invention relates to a novel process for the preparation ofmetal-containing compounds and to the use of these in electrodes forenergy storage devices and the like.

BACKGROUND OF THE INVENTION

Lithium-ion battery technology has enjoyed a lot of attention in recentyears and provides the preferred portable battery for most electronicdevices in use today. Such batteries are “secondary” or rechargeablewhich means they are capable of undergoing multiple charge/dischargecycles. Typically lithium-ion batteries are prepared using one or morelithium electrochemical cells containing electrochemically activematerials. Such cells comprise an anode (negative electrode), a cathode(positive electrode) and an electrolyte material. When a lithium-ionbattery is charging, Li⁺ ions de-intercalate from the cathode and insertinto the anode. Meanwhile charge balancing electrons pass from thecathode through the external circuit containing the charger and into theanode of the battery. During discharge the same process occurs but inthe opposite direction.

Various electrochemically active materials have been suggested for useas the cathode materials, for example LiCoO₂, LiMn₂O₄ and LiNiO₂, seeU.S. Pat. No. 5,135,732 and U.S. Pat. No. 4,246,253. However thesematerials exhibit problems, for example cycle fading (depletion incharge capacity over repeated charge/discharge cycles), which make themcommercially unattractive. Attempts to address cycle fading have led tolithium metal phosphate and lithium metal fluorophosphates becomingfavourable materials. Such materials were first reported in U.S. Pat.No. 6,203,946, U.S. Pat. No. 6,387,568, and by Goodenough et al. in“Phospho-olivines as Positive-Electrode Materials for RechargeableLithium Batteries”, Journal of Electrochemical Society, (1997) No. 144,pp 1188-1194.

Many workers have tried to provide economical and reproducible synthesismethods for phosphate-containing materials, and especially for highperformance (optimised) phosphate-containing materials. A review of theprior art methods which describe the preparation of one particularlithium metal phosphate, namely, lithium iron phosphate (LiFePO₄), isgiven by X. Zhang et al in “Fabrication and ElectrochemicalCharacteristics of LiFePO₄ Powders for Lithium-Ion Batteries”, KONAPowder and Particle Journal No. 28 (2010) pp 50-73. As this reviewdemonstrates, a lot of effort has been expended since lithium ironphosphate was first identified in 1997, to find the most expedientmethod for producing a LiFePO₄ material with the best all roundperformance; for example solid-state synthesis using mechanochemicalactivation to increase the activation of the starting materials,microwave heating to control the particle size of the active cathodematerial, and carbothermal reduction which enables Fe(III) e.g. in theform of Fe₂O₃ or FePO₄ (i.e. cheap and readily available sources ofiron) to be used as a precursor material. The carbothermal reductionprocess is a high-temperature reduction reaction (typically 550° C. to850° C.) which commonly utilizes carbon black, graphite or pyrolyzedorganic chemicals as the source of carbon reducing agent. Carbothermalreduction is a highly endothermic reaction; hence the reactiontemperature must be sufficient to drive the reaction. In addition, sincesolid carbon is used as the reducing agent, all the precursors andreactants must be kept in good contact throughout the reaction,nevertheless as reported in the review mentioned above, carbothermalreduction is excellent for the reduction of Fe(III), the stabilizationof Fe(II), the control of particle morphology, and the enhancement ofelectrical conductivity by coating LiFePO₄ with residual carbon.

Particulate reducing agents other than carbon, specifically siliconoxide, titanium oxide and elemental metals such as Fe, Co, Ni, Mn, Cu,V, Ti, Cr, Nb, Mo, Mg, Ca, Zn, Sr, Pb, Cd, Sn, Ba, Be, Al and B aredisclosed in EP1 343 720.

More recently US 2012/0061612 A1 discloses the synthesis of olivine-typelithium-containing phosphate compounds (LiMPO₄) using aphosphorus-source such as at least one selected from phosphates,hypophosphites, phosphites and metaphosphates. The described reactionprocess involves a two stage firing regime, in which a first firing stepis conducted at a temperature of higher than 400° C. and is for theremoval of the volatile components. Preferably this first firing step isconducted in an atmosphere that contains 1 volume % or more of oxygen,and to support this all of the Specific Examples in this prior art areconducted under an air atmosphere. No Specific Examples using ahypophosphite are given however, and if hypophosphite were to be used inair or a 1 volume % oxygen atmosphere, one would discover that underthese conditions the hypophosphite materials would oxidize to aphosphate material and that such a phosphate would have no effect in theprocess of the present invention.

The most interesting cathode materials are those which have large chargecapacity, are capable of good cycling performance, highly stable, and oflow toxicity and high purity. To be commercially successful, the cathodematerials must also be easily and affordably produced. This long list ofrequirements is difficult to fulfil but, as detailed in the reviewmentioned above, the active materials most likely to succeed are thosewith small particle size and narrow size distribution, with an optimumdegree of crystallinity, a high specific surface area and with uniformmorphology.

Materials containing hypophosphite ions (H₂PO₂ ⁻), such as sodiumhypophosphite (NaH₂PO₂) and ammonium hypophosphite (NH₄H₂PO₂) areavailable very cheaply and widely used as the in-situ reducing agent forelectroless plating baths; they reduce metal salts (e.g. nickel salts)to elemental metal (e.g. Ni) in the plating process. Other agents, forexample materials containing hydrosulfite ions, such as sodiumhydrosulfite (Na₂S₂O₄) (also referred to as sodium hyposulfite andsodium dithionite), sodium sulfite (Na₂SO₃), formaldehyde, dimethylamine borane (DMAB), hydrazine, aliphatic alcohols, trimethyl borane,and borohydride materials are also known to be powerful reducing agents.

The present invention aims to provide a fast, reliable and costeffective process for the preparation of metal-containing compounds andincluding but not limited to alkali metal-containing compounds.Advantageously, the process of the present invention aims to providemetal-containing compounds that meet the structural and alkali ioninsertion properties needed for commercially viable cathode activematerials. To this end, the present invention provides a solid stateprocess for the preparation of a metal-containing compound comprisingusing a reaction mixture comprising i) one or morehypophosphite-containing materials and ii) one or more metal-containingprecursor compounds.

In particular the present invention provides a solid state process forthe preparation of a metal-containing compound comprising forming areaction mixture comprising i) one or more metal-containing precursorcompounds and optionally one or more non-metal-containing reactants andii) one or more hypophosphite-containing materials; wherein one or moreof the hypophosphite-containing materials is used as an agent to reduceone or more of the metal-containing precursor compounds; and furtherwherein the process is performed in the absence of an oxidisingatmosphere.

The one or more metal-containing precursor compounds and the one or moremetal-containing compounds preferably comprise one or more metalsselected from alkali metals, transition metals, non-transition metals,alkaline earth metals and metalloids. In the context of this inventionthe term “metalloid” is an element with both metal and non-metalcharacteristics.

Ideally, the present invention provides a solid state process in whichthe metal-containing compound comprises one or more metals which have anaverage oxidation state which is lower than the average oxidation stateof the one or more metals in the metal-containing precursor compounds.Further ideally, one or more of the metal-containing compounds andmetal-containing precursor compounds comprise one or more transitionmetals. In this latter case, during the process of the presentinvention, one or more of the transition metals in the metal-containingprecursor compounds is reduced by one or more of thehypophosphite-containing materials to yield a metal-containing compoundwith one or more transition metals with a lower average oxidation statethan the average oxidation state of the one or more transition metals inthe metal-containing precursor compounds.

In a highly preferred solid state process, the present inventionproduces compounds containing one or more alkali metals. Such compoundsinclude alkali metal (metal)-containing compounds and may be producedfor example by forming a reaction mixture comprising i) one or moremetal-containing precursor compounds comprising alkali metals andoptionally further metal-containing precursor compounds comprising oneor more metals selected from transition metals and/or non transitionmetals and/or alkaline earth metals and/or metalloids, and furtheroptionally one or more non-metal-containing reactants, and ii) one ormore hypophosphite-containing materials; wherein one or more of thehypophosphite-containing materials are used as an agent to reduce one ormore of the metal-containing precursor compounds; and further whereinthe process is performed in the absence of an oxidising atmosphere.

The further metal-containing precursor compounds that comprise one ormore metals selected from transition metals and/or non transition metalsand/or alkaline earth metals and/or metalloids may also be usedespecially, but not exclusively, when the alkali metal-containingprecursor compound does not already comprise a transition metal, and/ornon-transition metal and/or alkaline earth metal and/or metalloid.

As described below, the alkali metal(metal)-containing compounds mayalternatively be produced by forming a reaction mixture comprising oneor more metal-containing precursor compounds and further optionally oneor more non-metal-containing reactants, and ii) one or more alkali metalhypophosphite-containing materials; wherein one or more of the alkalimetal hypophosphite-containing materials are used as an agent to reduceone or more of the metal-containing precursor compounds and to provide asource of alkali metal in the alkali metal (metal)-containing compounds;and further wherein the process is performed in the absence of anoxidising atmosphere.

A preferred solid state process of the present invention produces ametal-containing compound of the formula:

A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f)

and comprises the step of forming a mixture comprising i) one or moremetal-containing precursor compounds and optionally one or morenon-metal-containing reactants, and ii) one or morehypophosphite-containing materials;

wherein:

A is an alkali metal selected from one or more of lithium, sodium andpotassium;

M comprises one or more metals selected from transition metals,non-transition metals and metalloids;

(X_(c)Y_(d))_(e) is at least one first anion; and

Z is at least one second anion

wherein a≧0; b>0; c>0; d≧0; e>0 and f≧0;

wherein a, b, c, d, e and f are chosen to maintain electroneutrality;

and wherein one or more of the hypophosphite-containing materials isused as an agent to reduce at least a portion of one or more of themetal-containing precursor compounds;

and further wherein the process is performed in the absence of anoxidising atmosphere.

Desirably, the solid state process of the present invention produces ametal-containing compound, for example of the formulaA_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f), in which M comprises one or moretransition metals and/or non transition metals and/or alkaline earthmetals and/or metalloids which have an average oxidation state which islower than the average oxidation state of the one or more metals(transition metals and/or non transition metals and/or alkaline earthmetals and/or metalloids) in the metal-containing precursor compounds.

The most preferred metal-containing compounds produced by the solidstate process of the present invention are of the formula:

A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f)

wherein:

A is an alkali metal selected from one or more of lithium, sodium andpotassium;

M comprises one or more transition metals and optionally one or morefurther metals selected from non-transition metals and metalloids;

(X_(c)Y_(d))_(e) is at least one first anion; and

Z is at least one second anion

wherein a≧0; b>0; c>0; d≧0; e>0 and f≧0;

wherein a, b, c, d, e and f are chosen to maintain electroneutrality;

and wherein the process comprises forming a mixture comprising i) one ormore metal-containing precursor compounds and optionally one or morenon-metal-containing reactants, and ii) one or morehypophosphite-containing materials; wherein one or more of thehypophosphite-containing materials is used as an agent to reduce one ormore of the metal-containing precursor compounds;

and further wherein the process is performed in the absence of anoxidising atmosphere.

The addition of one or more hypophosphite-containing materials as areducing agent (e.g. they reduce the oxidation state of the metal,particularly a transition metal, of the metal-containing precursorcompounds), is crucial to the success of the invention and dependingupon the particular one or more metal-containing precursor compounds,and the desired final product, the hypophosphite-containing materialsmay additionally behave as a source of phosphorus in the final productand/or as a source of the alkali metal. For example, when the targetmetal-containing compound contains sodium and phosphorus, both of theseelements may potentially be obtained from sodium hypophosphite when thelatter is used as the reducing agent. The fact that the one or morehypophosphite-containing materials potentially acts as both the reducingagent and/or as a source of phosphorus and/or as a source of alkalimetal in the metal-containing compound is seen as one of the manyadvantages of the present invention.

In a particularly preferred process, alkali metal (metal)-containingcompounds are prepared. Such compounds may have the formulaA_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f) where A is one or more alkali metals, Mcomprises one or more transition metals and/or one or more nontransition metals and/or one or more alkaline earth metals and/or one ormore metalloids, and X, Y, and Z are as defined below. In such alkalimetal (metal)-containing compounds, a>0, b>0, d≧0, e>0 and f≧0.

In the reaction products produced by the solid state process of thepresent invention:

A preferably comprises one or more alkali metals selected from sodium,lithium and potassium;

M comprises one or more metals selected from transition metals such astitanium, vanadium, niobium, tantalum, hafnium, chromium, molybdenum,tungsten, manganese, iron, osmium, cobalt, nickel, palladium, platinum,copper, silver, gold, zinc, cadmium, aluminum, scandium, yttrium,zirconium, technetium, rhenium, ruthenium, rhodium, iridium, mercury,gallium, indium, tin, lead, bismuth and selenium, non transition metalsand alkaline earth metals such as magnesium, calcium, beryllium,strontium and barium, and metalloids such as boron, silicon, germanium,arsenic, antimony and tellurium;

X comprises one or more elements selected from titanium, vanadium,chromium, arsenic, molybdenum, tungsten, niobium, manganese, aluminum,selenium, boron, oxygen, carbon, silicon, phosphorus, nitrogen, sulfur,fluorine, chlorine, bromine and iodine.

Y comprises one or more halides, sulfur-containing groups,oxygen-containing groups and mixtures thereof;

Z is selected from one or more halides, hydroxide-containing groups andmixtures thereof.

Any hypophosphite-containing materials may be used in the presentinvention, however, preferably they are any one or a mixture ofmaterials selected from lithium hypophosphite (LiH₂PO₂), sodiumhypophosphite (NaH₂PO₂), ammonium hypophosphite (NH₄H₂PO₂) andhypophosphorus acid (H₃PO₂). The most preferred materials comprisesodium hypophosphite (NaH₂PO₂) and/or ammonium hypophosphite (NH₄H₂PO₂).

Desirable compounds of the formula A_(a)M_(b)(X_(c)O_(d))_(e)Z_(f)include, but are not limited to, those in which A is lithium and/orsodium, and in which the first anion (X_(c)Y_(d))_(e) comprises one ormore groups, preferably selected from phosphate, condensedpolyphosphate, sulfate, oxide, thiosulfate, sulfite, chlorate, bromate,oxyhalide, halide, silicate, arsenate, selenate, molybdate, vanadategroups and any oxyanion groups.

Compounds where X comprises phosphorus, for example in which(X_(c)Y_(d))_(e) is a PO₄ and/or P₂O₇ moiety are especially preferred.Similarly, compounds in which X comprises sulfur are equallyadvantageous, such as those containing SO₄ moieties.

Other favourable materials include:

LiFePO₄,

LiFePO₄/Fe₂P,

LiMnPO₄,

LiCoPO₄,

LiNiPO₄,

NaFePO₄,

NaMnPO₄,

NaCoPO₄,

NaNiPO₄,

LiMn_(0.5)Fe_(0.2)Mg_(0.3)PO₄,

Li₃V₂(PO₄)₃,

Na₄Fe₃(PO₄)₂P₂O₇,

Na₃V₂(PO₄)₃,

LiMn_(0.5)Fe_(0.5)PO₄,

Na₇V₄(P₂O₇)₄PO₄,

Na₇V₃(P₂O₇)₄,

Na₂Fe(SO₄)₂,

NaVPO₄F,

LiVPO₄F,

Na₃V(PO₄)₂,

Li₃V(PO₄)₂,

NaVOPO₄,

LiVOPO₄,

LiV₂O₅,

NaV₂O₅,

NaVO₂,

VPO₄,

MoP₂O₇,

MoOPO₄,

Fe₃(PO₄)₂,

Na_(8−2x)Fe_(4+x)(P₂O₇)₄,

Na_(8−2x)Mn_(4+x)(P₂O₇)₄,

Na₂MnP₂O₇,

Na₂FeP₂O₇,

Na₂CoP₂O₇,

Na₄Mn₃(PO₄)₂P₂O₇,

Na₄Co₃(PO₄)₂P₂O₇,

Na₄Ni₃(PO₄)₂P₂O₇,

NaFeSO₄F,

LiFeSO₄F,

NaMnSO₄F,

LiMnSO₄F,

Na₂FePO₄F,

Na₂MnPO₄F,

Na₂CoPO₄F,

Na₂NiPO₄F,

Na₂Fe₂(SO₄)₃,

Li₂Fe₂(SO₄)₃, and

Li₂Fe(SO₄)₂.

Advantageously, the present invention provides a solid state process forthe preparation of metal phosphate-containing materials (MPO₄)comprising using one or more hypophosphite-containing materials, (forexample sodium hypophosphite (NaH₂PO₂) and/or ammonium hypophosphite(NH₄H₂PO₂)) as an agent to reduce at one or more metal-containingprecursor compounds and optionally also as a source of phosphorus;wherein the process is performed in the absence of an oxidisingatmosphere.

In particular, the present invention provides a solid state process forthe preparation of a compound comprising an alkali metal (metal)phosphate of the general formula: AMPO₄, where A comprises one or morealkali metals; M comprises a metal selected from one or more ofmanganese, iron, cobalt, copper, zinc, nickel, magnesium and calcium,the process comprising forming a mixture of i) one or moremetal-containing precursor compounds and optionally one or morenon-metal-containing reactants and ii) one or morehypophosphite-containing materials; wherein one or more of thehypophosphite-containing materials is used as an agent for reducing atleast a portion of one or more of the metal-containing precursorcompounds and optionally also as a source of phosphorus and/or source ofalkali metal; further wherein the process is performed in the absence ofan oxidising atmosphere.

Preferred AMPO₄-containing compounds include NaMPO₄ and LiMPO₄;LiFePO₄-containing compounds are particularly preferred. These compoundsmay be produced in the solid state process of the present invention byforming a mixture comprising i) one or more metal-containing precursorcompounds and optionally one or more non-metal-containing reactants; andii) one or more hypophosphite-containing materials; wherein one or moreof the hypophosphite-containing materials are used as an agent to reduceone or more of the metal-containing precursor compounds, whereincomponent i) of the mixture may comprise one or more compounds selectedfrom LiH₂PO₄, Li₂HPO₄, LiOH, LiOH·H₂O, Fe₃O₄, Fe₂O₃, Li₂CO₃, FePO₄·xH₂O, FePO₄, Fe₃(PO₄)₂, FeSO₄·x H₂O, Fe(NO₃)₃, Fe(CH₃CO₂)₂, C₆H₈O₇ ·xFe³⁺·y NH₃ (ammonium iron (III) citrate), C₆H₅FeO₇ (iron (III) citrate)and Fe(C₅H₇O₂)₃ (iron (Ill) 2,4-petanedionate) and further wherein theprocess is performed in the absence of an oxidising atmosphere.

NaMPO₄ may be produced via a similar reaction process wherein themetal-containing precursor compounds may comprise one or more compoundsselected from NaH₂PO₄, Na₂HPO₄, NaOH, Fe₃O₄, Fe₂O₃, Na₂CO₃, FePO₄·x H₂O,FePO₄, Fe₃(PO₄)₂, FeSO₄·x H₂O, Fe(NO₃)₃, Fe(CH₃CO₂)₂, C₆H₈O₇ ·x Fe³⁺·yNH₃ (ammonium iron (III) citrate), C₆H₅FeO₇ (iron (III) citrate) andFe(C₅H₇O₂)₃ (iron (III) 2,4-petanedionate)

The reaction mixture in either case may also include any other suitablereagents and/or sources of phosphorus such as H₃PO₄, (NH₄)₂HPO₄,(NH₄)H₂PO₄.

A convenient way to perform the solid-state process of the presentinvention is by:

1. forming a mixture comprising i) one or more metal-containingprecursor compounds and optionally one or more non-metal-containingreactants, and ii) one or more hypophosphite-containing materials;

2. heating the mixture under a non-oxidizing atmosphere; and

3. recovering the resultant product, preferably a metal-containingcompound of the formula:

A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f)

wherein A is one or more alkali metals selected from lithium, sodium andpotassium, M comprises one or more metals selected from transitionmetals, non transition metals, alkaline earth metals and metalloids,(X_(c)Y_(d))_(e) is at least one first anion and z is at least onesecond anion, and wherein a≧0, b>0, c>0, d≧0, e>0 and f≧0.

Ideally the starting materials are intimately admixed in particulateform. This can be achieved using various methods, for example by finelygrinding the materials separately using a pestle and mortar or a ballmill, and then mixing them together, or the materials can be admixedwhilst they are being finely ground. The grinding and admixing is ofsufficient duration to produce a uniformly intermixed finely groundpowder. A solvent such as acetone or another material which is easilyremoved, for example a low boiling liquid, can be used to assist thegrinding/admixing process and this is preferably removed prior to theheating step. Other known techniques such as high energy ball millingand microwave activation may also be used to help prepare the startingmaterials, for example to increase their reactivity.

A key feature of the present invention is that it is a “solid-state”reaction i.e. a reaction in which all of the reactants are in solid formand are substantially free of any reaction medium such as a solvent.Where a solvent or other low boiling liquid is used to assist the mixingof the reactants, as described above, it is substantially removed priorto the heating step. Based on prior art knowledge, it is known thathypophosphite-containing materials are useful reducing agents whenemployed in alkaline solution reactions, particularly as the solublechemical reducing agent in electroless nickel and copper baths. However,the use of hypophosphite-containing materials is not yet known for thereduction of metals to intermediate oxidation states (i.e. not to themetallic state), and it is as yet unknown that they are effectivereducing agents for metals, particularly transition metals, other thancopper and nickel. Moreover, it is highly surprising thathypophosphite-containing materials are effective reducing agents insolid state reactions, and that in such reactions they can also providesome or all of the phosphate and/or the alkali metal component ofphosphate- and/or alkali metal-containing products.

The reaction between the starting materials generally occurs during theheating step of the process. This typically involves heating thereaction mixture either at a single temperature, or over a range oftemperatures, for example up to at least 150° C., preferably up to atleast 200° C. A single or a range of reaction temperatures of from 150°C. to 1200 ° C. is preferred with from 150° C. to 800° C. beingparticularly preferred.

Conveniently the reaction is performed under atmospheric pressure and itmust be conducted under a non-oxidising atmosphere, for examplenitrogen, argon or another inert gas, or under vacuum, and depending onthe target material and the precursors used, the reaction may also beperformed in a sealed reaction vessel. All of these reaction suchconditions are within the scope of the present invention and are all tobe included in the definition of “non-oxidizing atmosphere” and/or“absence of an oxidizing atmosphere”.

Advantageously, the reaction temperature is maintained for between 0.5and 12 hours, although the exact time will depend on the reactivity ofthe starting materials. Between 0.5 and 8 hours has been found to besufficient for many reactions utilising the process of the presentinvention.

As discussed above, in the process of the present invention the one ormore hypophosphite-containing materials are agents for the reduction ofthe average oxidation state of the metal (transition metal and/or nontransition metal and/or alkaline earth metal and/or metalloid) in theone or more metal-containing precursor compounds, and may additionallyprovide a source of phosphorus and/or a source of alkali metal.

In a preferred reaction scheme, lithium iron phosphate is preparedaccording to the process of the present invention from:

0.125 Li₂CO₃+0.25 NH₄H₂PO₂+0.75 LiH₂PO₄+0.5 Fe₂O₃→LiFePO₄+0.125 CO₂+0.25NH₃+1.125 H₂O

The metal-containing materials of formulaA_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f) prepared by the process of the presentinvention are suitable for use in many different applications, forexample as the active material in electrodes, particularly cathodes usedin energy storage devices, rechargeable batteries, electrochemicaldevices and electrochromic devices. This is especially the case foralkali metal (metal)-containing materials. Advantageously, theelectrodes made using the materials produced by the present inventionare used in conjunction with a counter electrode and one or moreelectrolyte materials. The electrolyte materials may be any conventionalor known materials and may comprise either aqueous electrolyte(s) ornon-aqueous electrolyte(s).

An inherent problem with a number of metal-containing compounds,especially alkali metal-containing compounds, is their low electricalconductivity. To address this problem it is known to add conductivematerials such as carbon-containing materials for example, graphite,carbon black, sucrose and acetylene black either to the startingmaterials, such as during grinding, or as a coating to the finalmetal-containing products. Other known conductive materials includemetal powders and other highly conductive inorganic materials.

It is therefore desirable, when making inherently non-conductivematerials such as alkali metal-containing compounds using the solidstate process of the present invention, to add/intimately disperse oneor more conductive materials such as carbon to the reaction mixtureand/or to one or more of the starting materials and/or to the finalproduct.

It is believed that the A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f) compoundsproduced by the process of the present invention may, where the startingmaterials so favour, be in the form of a composite material thatincludes a conductive compound which is preferably produced in situduring the reaction between the metal-containing precursor compounds andone or more hypophosphite-containing materials. The conductive compoundformed in situ is preferably a phosphorus-containing compound, and asuitable conductive material may comprise, at least in part, atransition metal phosphide- and/or a non-transition metal phosphide-and/or a metalloid phosphide-containing material such as, in the casewhere the metal component M comprises iron, an iron phosphide-containingmaterial, for example Fe₂P. This latter iron phosphide material inparticular, is known to be highly conductive.

Thus in a second aspect, the present invention provides a compositioncomprising a metal-containing compound e.g. of the formulaA_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f) as defined above, and one or moreconductive materials, wherein at least a portion of the one or moreconductive materials is formed in situ during the solid state processdescribed above, in particular when one or more of thehypophosphite-containing materials is used as an agent to reduce one ormore of the metal-containing precursor compounds. Desirably theinvention provides a composition comprising LiFePO₄ and at least oneconductive material comprising one or more phosphide-containingcompounds. Suitable phosphide-containing compounds may include, but arenot limited to binary phosphides.

Further, in a third aspect, the present invention provides a process forpreparing a composition comprising a metal-containing compound, e.g. ofthe formula A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f) defined as above, comprisingforming a reaction mixture comprising i) one or more metal-containingprecursor compounds and optionally one or more non-metal-containingreactants, and ii) one or more hypophosphite-containing materials;wherein one or more of the hypophosphite-containing materials is used asan agent to reduce one or more of the metal-containing precursorcompounds; and further wherein the process is conducted in the absenceof an oxidizing atmosphere.

In a fourth aspect, the present invention provides an electrode whichutilises active materials of formula A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f),prepared in accordance with the present invention as described above,especially an electrode which utilises a composition comprising suchactive materials in combination with a phosphorus-containing conductivematerial, and particularly a phosphorus-containing conductive materialwhich has been made, at least in part, during the reaction processdescribed above involving one or more hypophosphite-containingmaterials.

In a another aspect, the present invention provides a solid state methodfor the preparation of metal-containing compounds comprising forming amixture of i) one or more metal-containing precursor compounds and ii)one or more materials selected from hydrosulfite-containing materials,sulfite-containing materials, formaldehyde, dimethyl amine borane(DMAB), hydrazine and borohydride-containing materials.

The hydrosulfite-containing materials may comprise, for example, sodiumhydrosulfite (Na₂S₂O₄) (also referred to as sodium hyposulfite andsodium dithionite) or lithium hydrosulfite (Li₂S₂O₄), and thesulfite-containing materials may comprise, for example, sodium sulfite(Na₂SO₃) or lithium sulfite (Li₂SO₃). The latter sulfite-containingcompounds are used as reducing agents, however, they advantageously mayalso provide a source of the sulfur and/or alkali metal component of thereaction product, for example where the reaction product is an alkalimetal and/or sulfate-containing material. Thus the present inventionprovides a solid state process for the preparation of sulfate-containingmaterials comprising using one or more hydrosulfite-containing materialsand/or sulfite-containing materials as a reducing agent and additionallyas a source of sulfur and/or source of alkali metal. The reaction isperformed in the absence of an oxidising atmosphere.

In still further aspects, the present invention provides an energystorage device comprising an electrode as described above, for use asone or more of the following: a sodium ion and/or lithium ion and/orpotassium ion cell; a sodium metal and/or lithium metal and/or potassiummetal ion cell; a non-aqueous electrolyte sodium ion and/or lithium ionand/or potassium ion cell; and an aqueous electrolyte sodium ion and/orlithium ion and/or potassium ion cell. Specifically, the energy storagedevice may be a battery.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to thefollowing figures in which:

FIG. 1A shows the voltage profile (electrode potential versus cumulativespecific capacity) for LiFePO₄ active material produced according toExample 1 of the present invention;

FIG. 1B shows the differential capacity profile (differential capacityversus electrode potential) for LiFePO₄ active material producedaccording to Example 1 of the present invention;

FIG. 1C is an XRD profile for LiFePO₄ active material produced accordingto Example 1 of the present invention;

FIG. 2A shows the voltage profile (electrode potential versus cumulativespecific capacity) for LiFePO₄ active material produced according toExample 2 of the present invention;

FIG. 2B shows the differential capacity profile (differential capacityversus electrode potential) for LiFePO₄ active material producedaccording to Example 2 of the present invention;

FIG. 2C is an XRD profile for LiFePO₄ active material produced accordingto Example 2 of the present invention with impurities labeled asfollows: *Li₃PO₄, #FeP, ′Li₄P₂O₇, and ̂Fe₂P;

FIG. 3A shows the voltage profile (electrode potential versus cumulativespecific capacity) for LiFePO₄ active material produced according toExample 3 of the present invention;

FIG. 3B shows the differential capacity profile (differential capacityversus electrode potential) for LiFePO₄ active material producedaccording to Example 3 of the present invention;

FIG. 3C is an XRD profile for LiFePO₄ active material produced accordingto Example 3 of the present invention, with impurities labeled asfollows: * Li₄P₂O₇, # Fe₂O₃;

FIG. 4A shows the voltage profile (electrode potential versus cumulativespecific capacity) for LiFePO₄ active material produced according tocomparative Example 4;

FIG. 4B shows the differential capacity profile (differential capacityversus electrode potential) for LiFePO₄ active material producedaccording to comparative Example 4;

FIG. 4C is an XRD profile for LiFePO₄ active material produced accordingto comparative Example 4, with impurities labeled as follows: *Li₃PO₄,#NaFePO₄;

FIG. 5A shows the voltage profile (electrode potential versus cumulativespecific capacity) for LiFePO₄ active material produced according toExample 5;

FIG. 5B shows the differential capacity profile (differential capacityversus electrode potential) for LiFePO₄ active material producedaccording to comparative Example 5;

FIG. 5C is an XRD profile for LiFePO₄ active material produced accordingto comparative Example 5;

FIG. 6A shows the voltage profile (electrode potential versus cumulativespecific capacity) for Li_(1−x)Na_(x)FePO₄ active material producedaccording to Example 6 of the present invention;

FIG. 6B shows the differential capacity profile (differential capacityversus electrode potential) for Li_(1−x)Na_(x)FePO₄ active materialproduced according to Example 6 of the present invention;

FIG. 6C is an XRD profile for Li_(1−x)Na_(x)FePO₄ active materialproduced according to Example 6 of the present invention, withimpurities labeled as follows: *NaFePO₄;

FIG. 7A shows the voltage profile (electrode potential versus cumulativespecific capacity) for LiFePO₄ active material produced according toExample 7 (comparative);

FIG. 7B shows the differential capacity profile (differential capacityversus electrode potential) for LiFePO₄ active material producedaccording to Example 7 (comparative);

FIG. 7C is an XRD profile for LiFePO₄ active material produced accordingto Example 7 (comparative);

FIG. 8A shows the voltage profile (electrode potential versus cumulativespecific capacity) for LiFePO₄ active material produced according toExample 8 (comparative);

FIG. 8B shows the differential capacity profile (differential capacityversus electrode potential) for LiFePO₄ active material producedaccording to Example 8 (comparative);

FIG. 8C is an XRD profile for LiFePO₄ active material produced accordingto Example 8 (comparative);

FIG. 9A shows the voltage profile (electrode potential versus cumulativespecific capacity) for NaFePO₄ active material produced according toExample 9 of the present invention;

FIG. 9B shows the differential capacity profile (differential capacityversus electrode potential) for NaFePO₄ active material producedaccording to Example 9 of the present invention;

FIG. 9C is an XRD profile for NaFePO₄ active material produced accordingto Example 9 of the present invention, with impurities labeled asfollows: *Fe₃O₄, #Na₄P₂O₇;

FIG. 10A shows the voltage profile (electrode potential versuscumulative specific capacity) for Li₃V₂(PO₄)₃ active material producedaccording to Example 10 of the present invention;

FIG. 10B shows the differential capacity profile (differential capacityversus electrode potential) for Li₃V₂(PO₄)₃ active material producedaccording to Example 10 of the present invention;

FIG. 10C is an XRD profile for Li₃V₂(PO₄)₃ active material producedaccording to Example 10 of the present invention (asterisks denote peaksdue to LiVP₂O₇ impurity);

FIG. 11A shows the voltage profile (electrode potential versuscumulative specific capacity) for Na₇V₄(PO₄)(P₂O₇)₄ active materialproduced according to Example 11 of the present invention;

FIG. 11B shows the differential capacity profile (differential capacityversus electrode potential) for Na₇V₄(PO₄)(P₂O₇)₄ active materialproduced according to Example 11 of the present invention;

FIG. 11C is an XRD profile for Na₇V₄(PO₄)(P₂O₇)₄ active materialproduced according to Example 11 of the present, with impurities labeledas follows: *NaVP₂O₇;

FIG. 12A shows the voltage profile (electrode potential versuscumulative specific capacity) for Na₄Fe₃(PO₄)₂P₂O₇ active materialproduced according to Example 12 of the present invention;

FIG. 12B shows the differential capacity profile (differential capacityversus electrode potential) for Na₄Fe₃(PO₄)₂P₂O₇ active materialproduced according to Example 12 of the present invention;

FIG. 12C is an XRD profile for Na₄Fe₃(PO₄)₂P₂O₇ active material producedaccording to Example 12 of the present invention;

FIG. 13A shows the voltage profile (electrode potential versuscumulative specific capacity) for Na_(6.24)Fe_(4.88)(P₂O₇)₄ activematerial produced according to Example 13 of the present invention;

FIG. 13B shows the differential capacity profile (differential capacityversus electrode potential) for Na_(6.24)Fe_(4.88)(P₂O₇)₄ activematerial produced according to Example 13 of the present invention;

FIG. 13C is an XRD profile for Na_(6.24)Fe_(4.88)(P₂O₇)₄ active materialproduced according to Example 13 of the present, with impurities labeledas follows: *NaVP₂O₇;

DETAILED DESCRIPTION

General Method:

1) Intimately mix together the starting materials in the correctstoichiometric ratio and press into a pellet.

2) Heat the resulting mixture in a furnace under a non-oxidizingatmosphere, at a furnace temperature of between 300° C. and 800° C.until reaction product forms.

3) Allow the product to cool before grinding it to a powder.

The starting materials and reaction conditions used in Examples 1 to 13are summarised in Table 1 below:

TABLE 1 REACTION EXAMPLE STARTING MATERIALS TARGET PRODUCT CONDITIONS  10.375 Li₂CO₃ LiFePO₄ Mixing solvent: None. 0.75 NH₄H₂PO₂ (sample X0499,N₂, 600° C., dwell time 0.25 LiH₂PO₄ cell#205010) of 8 hours. 0.5 Fe₂O₃XRD scan 1.25 C parameters: 2θ = 5°-60° (3× amount of reducingIncrement: 0.05° power required, carbon in Speed: 2 secs/step the mix) 2 0.5 Li₂CO₃ LiFePO₄ Mixing solvent: None. 1 NH₄H₂PO₂ (sample X0500,N₂, 600° C., dwell time 0.5 Fe₂O₃ Cell #205011) of 8 hours. (4× amountof reducing XRD scan power required, no parameters: 2θ = 5°-60° carbonin the mix) Increment: 0.025° Speed: 1 sec/step  3 0.75 H₃PO₄ LiFePO₄Mixing solvent: Water. 0.25 H₃PO₂ (sample X0638, N₂, 400° C., dwell time0.50 Fe₂O₃ Cell #207046) of 8 hours. 1 LiOH•H₂O XRD scan (No carbon inthe parameters: 2θ = 5°-60° precursor mix, no excess Increment: 0.025°reducing power) Speed: 1 sec/step  4 0.125 Li₂CO₃ LiFePO₄ Mixingsolvent: 0.75 LiH₂PO₄ (sample X0877, Acetone. 0.5 Fe₂O₃ Cell # 210057)N₂, 600° C., dwell time of 0.25 NaH₂PO₂ XRD scan 6 hours. (NaH₂PO₂, noexcess parameters: 2θ = 5°-60° reducing power, no Increment: 0.025°carbon in mix) Speed: 1 sec/step  5 1 LiH₂PO₄ LiFePO₄ Mixing solvent:0.5 Fe₂O₃ (sample X0879, Acetone. 0.25 NaH₂PO₂ Cell #210059) N₂, 600°C., dwell time (NaH₂PO₂, no excess XRD scan of 6 hours. reducing power,no parameters: 2θ = 5°-60° carbon in mix) Increment: 0.025° Speed: 1sec/step  6 0.75 LiH₂PO₄ Li_(1-x)Na_(x)FePO₄ Mixing solvent: 0.5 Fe₂O₃(sample X0878, Acetone 0.25 NaH₂PO₂ Cell #210058) N₂, 600° C., dwelltime of (No excess reducing XRD scan 6 hours. power, no carbon in mix)parameters: 2θ = 5°-60° Increment: 0.025° Speed: 1 sec/step  7 1 LiH₂PO₄LiFePO₄ Mixing solvent: None Comparative 1 Fe(C₂O₄)•2H₂O (sample X0650,N₂, 750° C., dwell time Cell # 207072) of 8 hours. XRD scan parameters:2θ = 5°-60° Increment: 0.025° Speed: 1 sec/step  8 1 LiH₂PO₄ LiFePO₄Mixing solvent: None Comparative 0.5 Fe₂O₃ (sample X0649, N₂, 750° C.,dwell time of 1 C Cell # 207071) 8 hours. XRD scan parameters: 2θ =5°-60° Increment: 0.025° Speed: 1 sec/step  9 1 Na₄H₂PO₂ NaFePO₄ Mixingsolvent: Water 0.5 Fe₂O₃ (sample X0346 N₂, 550° C., dwell time (4×required amount of Cell # 202073) of 8 hours reducing power required,XRD scan no carbon in mix) parameters: 2θ = 5°-60° Increment: 0.015°Speed: 0.5 secs/step 10 1 Li₂CO₃ Li₃V₂(PO₄)₃ Mixing solvent: None 1LiH₂PO₄ (sample X0491 N₂, 700° C., dwell time 1 V₂O₅ Cell # 204079) of 8hours 1 NH₄H₂PO₄ XRD scan 1 NH₄H₂PO₂ parameters: 2θ = 5°-60° (No excessreducing Increment: 0.015° power, no carbon in mix) Speed: 0.5 secs/step11 7 NaH₂PO₄ Na₇V₄(PO₄)(P₂O₇)₄ Mixing solvent: None 2 NH₄H₂PO₂ (sampleX0458 N₂, 800° C., dwell time 2 V₂O₅ Cell # 204040) of 8 hours (Noexcess reducing power, XRD scan no carbon in mix) parameters: 2θ =5°-60° Increment: 0.015° Speed: 0.5 secs/step 12 1 NaH₂PO₂Na₄Fe₃(PO₄)₂P₂O₇ Mixing solvent: 1.5 Na₂CO₃ (sample X0996 Acetone 3FePO₄ Cell # 212015 N₂, 600° C., dwell time (NaH₂PO₂ (33% excess XRDscan of 6 hours reducing power), no carbon parameters: 2θ = 5°-60° inmix) Increment: 0.025° Speed: 1 sec/step 13 5.02 NaH₂PO₄Na_(6.24)Fe_(4.88)(P₂O₇)₄ Mixing solvent: 1.22 NaH₂PO₂ Sample X0990Acetone 2.40 Fe₂O₃ Cell #212008 N₂, 600° C., dwell time 1.76 NH₄H₂PO₄XRD scan of 8 hours (NaH₂PO₂ (no excess parameters: 2θ = 5°-60° reducingpower), no carbon Increment: 0.025° Speed: in mix) 1 sec/step

Product Analysis using XRD

Analysis by X-ray diffraction techniques was conducted using a SiemensD5000 powder diffractometer to confirm that the desired target materialshad been prepared, to establish the phase purity of the product materialand to determine the types of impurities present. From this informationit is possible to determine the unit cell lattice parameters.

The general XRD operating conditions used to analyse the precursorelectrode materials are as follows:

Slits sizes: 1 mm, 1 mm, 0.1 mm

Range: 2θ=5°-60°

X-ray Wavelength=1.5418 A (Cu Kα)

Speed: 0.5 to 2 seconds/step

Increment: 0.015° to 0.05°

Electrochemical Results

The target materials were tested in a metallic lithium half cell whichcan be made using the following procedure:

Generic Procedure to Make a Lithium Metal Electrochemical Test Cell

The positive electrode is prepared by solvent-casting a slurry of theactive material, conductive carbon, binder and solvent. The conductivecarbon used is Super P (Timcal). PVdF co-polymer (e.g. Kynar Flex 2801,Elf Atochem Inc.) is used as the binder, and acetone is employed as thesolvent. The slurry is then cast onto glass and a free-standingelectrode film is formed as the solvent evaporates. The electrode isthen dried further at about 80° C. The electrode film contains thefollowing components, expressed in percent by weight: 80% activematerial, 8% Super P carbon, and 12% Kynar 2801 binder. Optionally, analuminum current collector may be used to contact the positiveelectrode. Metallic lithium on a copper current collector may beemployed as the negative electrode. The electrolyte comprises one of thefollowing: (i) a 1 M solution of LiPF₆ in ethylene carbonate (EC) anddimethyl carbonate (DMC) in a weight ratio of 1:1; (ii) a 1 M solutionof LiPF₆ in ethylene carbonate (EC) and diethyl carbonate (DEC) in aweight ratio of 1:1; or (iii) a 1 M solution of LiPF₆ in propylenecarbonate (PC) A glass fibre separator (Whatman, GF/A) or a porouspolypropylene separator (e.g. Celgard 2400) wetted by the electrolyte isinterposed between the positive and negative electrodes.

Cell Testing

The cells are tested as follows, using Constant Current Cyclingtechniques.

The cell is cycled at a given current density between pre-set voltagelimits. A commercial battery cycler from Maccor Inc. (Tulsa, Okla., USA)is used. On charge, sodium (lithium)-ions are extracted from the cathodeactive material. During discharge, lithium (sodium)-ions are re-insertedinto the cathode active material.

Example 1

FIGS. 1A and 1B (Cell#205010) show the first cycle constant current datafor the LiFePO₄ cathode active material (X0499, made using the reducingagent, ammonium hypophosphite, NH₄H₂PO₂) measured in a metallic lithiumhalf-cell. The reaction mixture also had carbon included as a conductiveadditive. FIG. 1A shows the voltage profile (electrode potential versuscumulative specific capacity) and FIG. 1B shows the differentialcapacity profile (differential capacity versus electrode potential). Theconstant current data shown in the figure were collected using a lithiummetal counter electrode at a current density of 0.04 mA/cm² betweenvoltage limits of 2.0 and 4.2 V. The non-aqueous electrolyte used was a1 M solution of LiPF₆ in a 1:1 mixture of ethylene carbonate (EC) anddiethyl carbonate (DEC). The electrochemical testing was carried out ata controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.113 V vs. Li.Referring to FIG. 1A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 142 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 131 mAh/g,indicating the general reversibility of the lithium-ion insertionreactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe excellent reversibility of the system. This is further exemplifiedby the symmetrical nature of the differential capacity profile shown inFIG. 1B.

Example 2

FIGS. 2A and 2B (Cell#205011) show the first cycle constant current datafor the LiFePO₄ cathode active material (X0500, made using the reducingagent, ammonium hypophosphite, NH₄H₂PO₂) measured in a metallic lithiumhalf-cell. FIG. 2A shows the voltage profile (electrode potential versuscumulative specific capacity) and FIG. 2B shows the differentialcapacity profile (differential capacity versus electrode potential). Theconstant current data shown in the figure were collected using a lithiummetal counter electrode at a current density of 0.04 mA/cm² betweenvoltage limits of 2.0 and 4.2 V. The non-aqueous electrolyte used was a1 M solution of LiPF₆ in a 1:1 mixture of ethylene carbonate (EC) anddiethyl carbonate (DEC). The electrochemical testing was carried out ata controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.029 V vs. Li.Referring to FIG. 2A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 107 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 83 mAh/g,indicating the general reversibility of the lithium-ion insertionreactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe reversibility of the system. This is further exemplified by thesymmetrical nature of the differential capacity profile shown in FIG.2B.

Example 3

FIGS. 3A and 3B (Cell#207046) show the first cycle constant current datafor the LiFePO₄ cathode active material (X0638, made using the reducingagent, hypophosphorous acid H₃PO₂) measured in a metallic lithiumhalf-cell. FIG. 3A shows the voltage profile (electrode potential versuscumulative specific capacity) and

FIG. 3B shows the differential capacity profile (differential capacityversus electrode potential). The constant current data shown in thefigure were collected using a lithium metal counter electrode at acurrent density of 0.04 mA/cm² between voltage limits of 2.5 and 4.2 V.The non-aqueous electrolyte used was a 1 M solution of LiPF₆ in a 1:1mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Theelectrochemical testing was carried out at a controlled temperature of25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.287 V vs. Li.Referring to FIG. 3A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 98 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 84 mAh/g,indicating the general reversibility of the lithium-ion insertionreactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe reversibility of the system. This is further exemplified by thesymmetrical nature of the differential capacity profile shown in FIG.3B.

Example 4

FIGS. 4A and 4B (Cell#210057) show the first cycle constant current datafor the LiFePO₄ cathode active material (X0877, made using the reducingagent, sodium hypophosphite, NaH₂PO₂ and assuming a Na₂O by-product)measured in a metallic lithium half-cell. FIG. 4A shows the voltageprofile (electrode potential versus cumulative specific capacity) andFIG. 4B shows the differential capacity profile (differential capacityversus electrode potential). The constant current data shown in thefigure were collected using a lithium metal counter electrode at acurrent density of 0.04 mA/cm² between voltage limits of 2.5 and 4.2 V.The non-aqueous electrolyte used was a 1 M solution of LiPF₆ in a 1:1mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Theelectrochemical testing was carried out at a controlled temperature of25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.038 V vs. Li.Referring to FIG. 4A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 123 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 104 mAh/g,indicating the general reversibility of the lithium-ion insertionreactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe reversibility of the system. This is further exemplified by thesymmetrical nature of the differential capacity profile shown in FIG.4B.

Example 5

FIGS. 5A and 5B (Cell#210059) show the first cycle constant current datafor the LiFePO₄ cathode active material (X0879, made using the reducingagent, sodium hypophosphite, NaH₂PO₂ and assuming a NaPO₃ by-product)measured in a metallic lithium half-cell. FIG. 5A shows the voltageprofile (electrode potential versus cumulative specific capacity) andFIG. 5B shows the differential capacity profile (differential capacityversus electrode potential). The constant current data shown in thefigure were collected using a lithium metal counter electrode at acurrent density of 0.04 mA/cm² between voltage limits of 2.5 and 4.2 V.The non-aqueous electrolyte used was a 1 M solution of LiPF₆ in a 1:1mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Theelectrochemical testing was carried out at a controlled temperature of25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.145 V vs. Li.Referring to FIG. 5A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 102 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 85 mAh/g,indicating the general reversibility of the lithium-ion insertionreactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe reversibility of the system. This is further exemplified by thesymmetrical nature of the differential capacity profile shown in FIG.5B.

Example 6

FIGS. 6A and 6B (Cell#210058) show the first cycle constant current datafor the Li_(1−x)Na_(x)FePO₄ cathode active material (X0878, made usingthe reducing agent, sodium hypophosphite, NaH₂PO₂) measured in ametallic lithium half-cell. FIG. 6A shows the voltage profile (electrodepotential versus cumulative specific capacity) and FIG. 6B shows thedifferential capacity profile (differential capacity versus electrodepotential).

The constant current data shown in the figure were collected using alithium metal counter electrode at a current density of 0.04 mA/cm²between voltage limits of 2.5 and 4.2 V. The non-aqueous electrolyteused was a 1 M solution of LiPF₆ in a 1:1 mixture of ethylene carbonate(EC) and diethyl carbonate (DEC). The electrochemical testing wascarried out at a controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.012 V vs. Li.Referring to FIG. 6A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 117 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 100 mAh/g,indicating the general reversibility of the lithium-ion insertionreactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe reversibility of the system. This is further exemplified by thesymmetrical nature of the differential capacity profile shown in FIG.6B.

Example 7 (Comparative)

FIGS. 7A and 7B (Cell#207072) show the first cycle constant current datafor the LiFePO₄ cathode active material (X0650, made from iron oxalate,Fe(C₂O₄)·2 H₂O—an Fe²⁺ precursor that requires no reducing agent)measured in a metallic lithium half-cell. FIG. 7A shows the voltageprofile (electrode potential versus cumulative specific capacity) andFIG. 7B shows the differential capacity profile (differential capacityversus electrode potential). The constant current data shown in thefigure were collected using a lithium metal counter electrode at acurrent density of 0.04 mA/cm² between voltage limits of 2.5 and 4.2 V.The non-aqueous electrolyte used was a 1 M solution of LiPF₆ in a 1:1mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Theelectrochemical testing was carried out at a controlled temperature of25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.177 V vs. Li.Referring to FIG. 7A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 63 mAh/g wasobtained for the cathode active material. This is a relatively lowmaterial utilization. The subsequent re-insertion process correspondedto material specific capacity of 45 mAh/g indicating the relatively poorreversibility. FIG. 7B shows the corresponding differential capacityprofile for this material which is indistinct and noisy indicating thepoor electrochemical reversibility of the active material.

Example 8 (Comparative)

FIGS. 8A and 8B (Cell#207071) show the first cycle constant current datafor the LiFePO₄ cathode active material (X0649, made from Fe₂O₃ bycarbothermal reduction using Super P Carbon (Timcal) as the reducingagent and conductivity enhancer) measured in a metallic lithiumhalf-cell. FIG. 8A shows the voltage profile (electrode potential versuscumulative specific capacity) and FIG. 8B shows the differentialcapacity profile (differential capacity versus electrode potential). Theconstant current data shown in the figure were collected using a lithiummetal counter electrode at a current density of 0.04 mA/cm² betweenvoltage limits of 2.5 and 4.2 V. The non-aqueous electrolyte used was a1 M solution of LiPF₆ in a 1:1 mixture of ethylene carbonate (EC) anddiethyl carbonate (DEC). The electrochemical testing was carried out ata controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.177 V vs. Li.Referring to FIG. 8A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 135 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 111 mAh/gindicating good reversibility.

The symmetrical nature of the charge-discharge voltage profile furtherindicates the reversibility of the system. This is further exemplifiedby the symmetrical nature of the differential capacity profile shown inFIG. 8B.

Example 9

FIGS. 9A and 9B (Cell#202073) show the first cycle constant current datafor the NaFePO₄ cathode active material (X0346B, made using the reducingagent, sodium hypophosphite, NaH₂PO₂) measured in a metallic lithiumhalf-cell. FIG. 9A shows the voltage profile (electrode potential versuscumulative specific capacity) and FIG. 9B shows the differentialcapacity profile (differential capacity versus electrode potential). Theconstant current data shown in the figure were collected using a lithiummetal counter electrode at a current density of 0.04 mA/cm² betweenvoltage limits of 2.0 and 4.2 V. The non-aqueous electrolyte used was a1 M solution of LiPF₆ in a 1:1 mixture of ethylene carbonate (EC) anddiethyl carbonate (DEC). The electrochemical testing was carried out ata controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 2.804 V vs. Li.Referring to FIG. 9A, it is assumed that sodium ions are extracted fromthe active material during the initial charging of the cell. During thesodium ion extraction process, a charge equivalent to a materialspecific capacity of 24 mAh/g was obtained for the cathode activematerial. It is expected from thermodynamic considerations that thesodium extracted from the NaFePO₄ material during the initial chargingprocess, enters the electrolyte, and is then displacement ‘plated’ ontothe lithium metal anode (i.e. releasing more lithium into theelectrolyte). Therefore, during the subsequent discharging of the cell,it is assumed that a mix of lithium and sodium is re-inserted into thematerial. The re-insertion process corresponds to 23 mAh/g, indicatingthe reversibility of the ion insertion reactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe reversibility of the system. This is further exemplified by thesymmetrical nature of the differential capacity profile shown in FIG.9B.

Example 10

FIGS. 10A and 10B (Cell#204079) show the first cycle constant currentdata for the Li₃V₂(PO₄)₃ cathode active material (X0491, made using thereducing agent, ammoinium hypophosphite, NH4H₂PO₂) measured in ametallic lithium half-cell. FIG. 10A shows the voltage profile(electrode potential versus cumulative specific capacity) and FIG. 10Bshows the differential capacity profile (differential capacity versuselectrode potential). The constant current data shown in the figure werecollected using a lithium metal counter electrode at a current densityof 0.04 mA/cm² between voltage limits of 2.8 and 4.3 V. The non-aqueouselectrolyte used was a 1 M solution of LiPF₆ in a 1:1 mixture ofethylene carbonate (EC) and diethyl carbonate (DEC). The electrochemicaltesting was carried out at a controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 3.054 V vs. Li.Referring to FIG. 10A, during the first lithium extraction process, acharge equivalent to a material specific capacity of 103 mAh/g wasobtained for the cathode active material. The subsequent re-insertionprocess corresponded to material specific capacity of 83 mAh/g,indicating the general reversibility of the lithium-ion insertionreactions.

The symmetrical nature of the charge-discharge voltage profile indicatesthe reversibility of the system. This is further exemplified by thesymmetrical nature of the differential capacity profile shown in FIG.10B.

Example 11

FIGS. 11A and 11B (Cell#204040) show the first cycle constant currentdata for the Na₇V₄(P₂O₇)₄PO₄ cathode active material (X0458, made usingthe reducing agent, ammonium hypophosphite, NH₄H₂PO₂) measured in ametallic lithium half-cell. FIG. 11A shows the voltage profile(electrode potential versus cumulative specific capacity) and FIG. 11Bshows the differential capacity profile (differential capacity versuselectrode potential). The constant current data shown in the figure werecollected using a lithium metal counter electrode at a current densityof 0.04 mA/cm² between voltage limits of 3.0 and 4.4 V. The non-aqueouselectrolyte used was a 1 M solution of LiPF₆ in a 1:1 mixture ofethylene carbonate (EC) and diethyl carbonate (DEC). The electrochemicaltesting was carried out at a controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 2.941 V vs. Li.Referring to FIG. 11A, it is assumed that sodium ions are extracted fromthe Na₇V₄(P₂O₇)₄PO₄ active material during the initial charging of thecell. During the sodium ion extraction process, a charge equivalent to amaterial specific capacity of 74 mAh/g was obtained for the cathodeactive material. It is expected from thermodynamic considerations thatthe sodium extracted from the material during the initial chargingprocess, enters the electrolyte, and is then displacement ‘plated’ ontothe lithium metal anode (i.e. releasing more lithium into theelectrolyte). Therefore, during the subsequent discharging of the cell,it is assumed that a mix of lithium and sodium is re-inserted into thematerial. The re-insertion process corresponds to 63 mAh/g, indicatingthe reversibility of the ion insertion reactions. The symmetrical natureof the charge-discharge voltage profile indicates the reversibility ofthe system. This is further exemplified by the symmetrical nature of thedifferential capacity profile shown in FIG. 11B.

Example 12

FIGS. 12A and 12B (Cell#212015) show the first cycle constant currentdata for the Na₄Fe₃(PO₄)₂P₂O₇ cathode active material (X0996, made usingthe reducing agent, sodium hypophosphite, NaH₂PO₂) measured in ametallic lithium half-cell.

FIG. 12A shows the voltage profile (electrode potential versuscumulative specific capacity) and FIG. 12B shows the differentialcapacity profile (differential capacity versus electrode potential). Theconstant current data shown in the figure were collected using a lithiummetal counter electrode at a current density of 0.02 mA/cm² betweenvoltage limits of 2.5 and 3.8 V. The non-aqueous electrolyte used was a1 M solution of LiPF₆ in a 1:1 mixture of ethylene carbonate (EC) anddiethyl carbonate (DEC). The electrochemical testing was carried out ata controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 2.843 V vs. Li.Referring to FIG. 12A, it is assumed that sodium ions are extracted fromthe active Na₄Fe₃(PO₄)₂P₂O₇ material during the initial charging of thecell. During the sodium ion extraction process, a charge equivalent to amaterial specific capacity of 63 mAh/g was obtained for the cathodeactive material. It is expected from thermodynamic considerations thatthe sodium extracted from the material during the initial chargingprocess, enters the electrolyte, and is then displacement ‘plated’ ontothe lithium metal anode (i.e. releasing more lithium into theelectrolyte). Therefore, during the subsequent discharging of the cell,it is assumed that a mix of lithium and sodium is re-inserted into thematerial. The re-insertion process corresponds to 52 mAh/g, indicatingthe reversibility of the ion insertion reactions. The symmetrical natureof the charge-discharge voltage profile indicates the reversibility ofthe system. This is further exemplified by the symmetrical nature of thedifferential capacity profile shown in FIG. 12B.

Example 13

FIGS. 13A and 13B (Cell#212008) show the first cycle constant currentdata for the Na_(6.24)Fe_(4.88)(P₂O₇)₄ cathode active material (X0990,made using the reducing agent, sodium hypophosphite, NaH₂PO₂) measuredin a metallic lithium half-cell.

FIG. 13A shows the voltage profile (electrode potential versuscumulative specific capacity) and FIG. 13B shows the differentialcapacity profile (differential capacity versus electrode potential). Theconstant current data shown in the figure were collected using a lithiummetal counter electrode at a current density of 0.02 mA/cm² betweenvoltage limits of 2.5 and 4.4 V. The non-aqueous electrolyte used was a1 M solution of LiPF₆ in a 1:1 mixture of ethylene carbonate (EC) anddiethyl carbonate (DEC). The electrochemical testing was carried out ata controlled temperature of 25° C.

The Open Circuit Voltage (OCV) of the as-made cell was 2.922 V vs. Li.Referring to FIG. 13A, it is assumed that sodium ions are extracted fromthe active Na_(6.24)Fe_(4.88)(P₂O₇)₄ material during the initialcharging of the cell. During the sodium ion extraction process, a chargeequivalent to a material specific capacity of 83 mAh/g was obtained forthe cathode active material. It is expected from thermodynamicconsiderations that the sodium extracted from the material during theinitial charging process, enters the electrolyte, and is thendisplacement ‘plated’ onto the lithium metal anode (i.e. releasing morelithium into the electrolyte). Therefore, during the subsequentdischarging of the cell, it is assumed that a mix of lithium and sodiumis re-inserted into the material. The re-insertion process correspondsto 83 mAh/g, indicating the reversibility of the ion insertionreactions. The symmetrical nature of the charge-discharge voltageprofile indicates the reversibility of the system. This is furtherexemplified by the symmetrical nature of the differential capacityprofile shown in FIG. 13B.

1. A solid state process for the preparation of a metal-containingcompound comprising forming a mixture comprising i) one or moremetal-containing precursor compounds and optionally one or morenon-metal-containing reactants, and ii) one or morehypophosphite-containing materials; wherein one or more of thehypophosphite-containing materials are used as an agent to reduce one ormore of the metal-containing precursor compounds; and further whereinthe process is performed in the absence of an oxidising atmosphere.
 2. Asolid state process according to claim 1 wherein the one or moremetal-containing precursor compounds comprise one or more metalsselected from transition metals, alkali metals, alkaline earth metals,non-transition metals and metalloids.
 3. A solid state process accordingto claim 1 or 2 wherein one or more of the metals in themetal-containing precursor compounds is reduced by one or more of thehypophosphite-containing materials such that the average oxidation stateof the one or more metals in the metal-containing compound is lower thanthe average oxidation state of the one or more metals in themetal-containing precursor compounds.
 4. A solid state process accordingto any of claims 1 to 3 for the preparation of an alkali metal(metal)-containing compound wherein at least one of the metal-containingprecursor compounds comprises at least one alkali metal.
 5. A solidstate process for preparing a compound comprising the formula:A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f) comprising forming a mixture comprisingi) one or more metal-containing precursor compounds and optionally oneor more non-metal-containing reactants and ii) one or morehypophosphite-containing materials; wherein one or more of thehypophosphite-containing materials are used as an agent to reduce one ormore of the metal-containing precursor compounds; wherein: A is analkali metal selected from one or more of lithium, sodium and potassium;M comprises one or more metals selected from transition metals and/ornon-transition metals and/or alkaline earth metals and/or metalloids;(X_(c)Y_(d))_(e) is at least one first anion; and Z is at least onesecond anion wherein a≧0; b>0; c>0; d≧0; e>0 and f≧0; wherein a, b, c,d, e and f are chosen to maintain electroneutrality; and further whereinthe process is performed in the absence of an oxidising atmosphere.
 6. Asolid state process according to claim 5 wherein M is a metal selectedfrom one or more of titanium, vanadium, niobium, tantalum, hafnium,chromium, molybdenum, tungsten, manganese, iron, osmium, cobalt, nickel,palladium, platinum, copper, silver, gold, zinc, cadmium, aluminum,scandium, yttrium, zirconium, technetium, rhenium, ruthenium, rhodium,iridium, mercury, gallium, indium, tin, lead, bismuth, selenium,magnesium, calcium, beryllium, strontium and barium, boron, silicon,germanium, arsenic, antimony and tellurium.
 7. A solid state processaccording to claim 5 wherein X comprises one or more elements selectedfrom titanium, vanadium, chromium, arsenic, molybdenum, tungsten,niobium, manganese, aluminum, selenium, boron, oxygen, carbon, silicon,phosphorus, nitrogen, sulfur, fluorine, chlorine, bromine and iodine. 8.A solid state process according to claim 5 wherein Y is selected fromone or more halides, sulfur-containing groups, oxygen-containing groupsand mixtures thereof.
 9. A solid state process according to claim 5wherein Z is selected from one or more halides, hydroxide-containinggroups and mixtures thereof.
 10. A solid state process according toclaim 5 wherein X comprises phosphorus.
 11. A solid state processaccording to claim 10 wherein (X_(c)Y_(d))_(e) is a moiety selected fromone or more of PO₄ and/or P₂O₇.
 12. A solid state process according toclaim 5 wherein X comprises sulfur.
 13. A solid state process accordingto claim 12 wherein (X_(c)Y_(d))_(e) is a SO₄ moiety.
 14. A solid stateprocess according to claims 1 to 13 for preparing metal-containingcompounds comprising LiFePO₄, LiFePO₄/Fe₂P, LiMnPO₄, LiCoPO₄, LiNiPO₄,NaFePO₄, NaMnPO₄, NaCoPO₄, NaNiPO₄, LiMn_(0.5)Fe_(0.2)Mg_(0.3)PO₄,Li₃V₂(PO₄)₃, Na₄Fe₃(PO₄)₂P₂O₇, Na₃V₂(PO₄)₃, LiMn_(0.5)Fe_(0.5)PO₄,Na₇V₄(P₂O₇)₄PO₄, Na₇V₃(P₂O₇)₄, Na₂Fe(SO₄)₂, NaVPO₄F, LiVPO₄F,Na₃V(PO₄)₂, Li₃V(PO₄)₂, NaVOPO₄, LiVOPO₄, LiV₂O₅, NaV₂O₅, NaVO₂, VPO₄,MoP₂O₇, MoOPO₄, Fe₃(PO₄)₂, Na_(8−2x)Fe_(4+x)(P₂O₇)₄,Na_(8−2x)Mn₄+_(x)(P₂O₇)₄, Na₂MnP₂O₇, Na₂FeP₂O₇, Na₂CoP₂O₇,Na₄Mn₃(PO4)2P₂O₇, Na₄Co₃(PO₄)₂P₂O₇, Na₄Ni₃(PO₄)2P₂O₇, NaFeSO₄F,LiFeSO₄F, NaMnSO₄F, LiMnSO₄F, Na₂Fe₂(SO₄)₃, Li₂Fe₂(SO₄)₃, Li₂Fe(SO₄)₂,Na₂FePO₄F, Na₂MnPO₄F, Na₂CoPO₄F and Na₂NiPO₄F.
 15. A solid state processfor the preparation of metal-containing compounds comprising forming amixture of i) one or more metal-containing precursor compounds andoptionally one or more non-metal-containing precursor compounds and ii)one or more hypophosphite-containing materials; wherein one or more ofthe hypophosphite-containing materials is used as an agent to reduce oneor more of the metal-containing precursor compounds and optionally alsoas a source of phosphorus and/or source of alkali metal; further whereinthe process is performed in the absence of an oxidising atmosphere. 16.A solid state process for the preparation of metal phosphate-containingcompounds comprising using one or more hypophosphite-containingmaterials as a reducing agent and optionally also as a source ofphosphorus and/or source of alkali metal; wherein the process isperformed in the absence of an oxidising atmosphere.
 17. A solid stateprocess for making an alkali metal phosphate-containing compoundcomprising forming a reaction mixture comprising i) a metal-containingprecursor compound wherein the metal is selected from one or more ofmanganese, iron, cobalt, nickel, copper, zinc, magnesium and calcium andoptionally one or more non-metal-containing reactants, and ii) one ormore materials comprising hypophosphite ions; wherein one or more of thematerials comprising hypophosphite ions are used as a reducing agent andoptionally also as a source of phosphorus and/or source of alkali metal;and wherein the process is performed in the absence of an oxidizingatmosphere.
 18. A solid state process according to claim 17 wherein thealkali metal phosphate has the general formula LiMPO₄ where M is a metalselected from one or more of manganese, iron, cobalt, nickel, copper,zinc, magnesium and calcium .
 19. A solid state process according to anyof claims 1 to 18 for the preparation of LiFePO₄ compounds comprisingforming a mixture of i) one or more metal-containing precursor compoundsselected from LiH₂PO₄, Fe₂O₃, Li₂CO₃, Li₂HPO₄, LiOH, LiOH·H₂O, Fe₃O₄,FePO₄·x H₂O, FePO₄, Fe₃(PO₄)₂, FeSO₄·x H₂O, Fe(NO₃)₃, Fe(CH₃CO₂)₂,C₆H₈O₇·x Fe³⁺·y NH₃ (ammonium iron (III) citrate), C₆H₅FeO₇ (iron (III)citrate) and Fe(C₅H₇O₂)₃ (iron (III) 2,4-petanedionate); and ii) one ormore hypophosphite-containing materials; wherein one or more of thehypophosphite-containing materials are used as an agent to reduce one ormore of the metal-containing precursor compounds.
 20. A solid stateprocess according to any of claims 1 to 17 for the preparation ofNaFePO₄ compounds comprising forming a mixture of i) one or moremetal-containing precursor compounds selected from NaH₂PO₄, Fe₂O₃,Na₂CO₃, Na₂HPO₄, NaOH, Fe₃O₄, FePO₄·x H₂O, FePO₄, Fe₃(PO₄)₂, FeSO₄·xH₂O, Fe(NO₃)₃, Fe(CH₃CO₂)₂, C₆H₈O₇·x Fe³⁺·y NH₃ (ammonium iron (III)citrate), C₆H₅FeO₇ (iron (III) citrate), Fe(C₅H₇O₂)₃ and (iron (III)2,4-petanedionate; and ii) one or more hypophosphite-containingmaterials; wherein one or more of the hypophosphite-containing materialsare used as an agent to reduce one or more of the metal-containingprecursor compounds.
 21. A solid state process according to anypreceding claim comprising the steps of: a) forming a mixture comprisingi) one or more metal-containing precursor compounds and optionally oneor more non-metal-containing reactants and ii) one or morehypophosphite-containing materials; b) heating the mixture in theabsence of an oxidizing atmosphere; and c) recovering the resultantproduct.
 22. A solid state process according to any of claims 1 to 21wherein the one or more hypophosphite-containing materials comprise anyone or a mixture of materials selected from lithium hypophosphite(LiH₂PO₂), sodium hypophosphite (NaH₂PO₂), ammonium hypophosphite(NH₄H₂PO₂) and hypophosphorus acid (H₃PO₂).
 23. A solid state processaccording to any of claims 1 to 21 further comprising the addition ofone or more conductive materials.
 24. A composition comprising a) acompound of formula A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f) prepared accordingto the process of any of claims 1-22 and b) one or more conductivematerials, wherein at least a portion of the one or more conductivematerials is formed in situ during the solid state process according toany one of claims 1-23.
 25. A composition according to claim 24 whereinat least one of the conductive materials formed in situ comprisesphosphorus.
 26. A composition according to claim 25 wherein at least oneof the conductive materials formed in situ comprises one or more of atransition metal phosphide, a non-transition metal phosphide, alkalineearth metal phosphide and a metalloid phosphide.
 27. A compositionaccording to claim 26 comprising LiFePO₄ and at least one conductivematerial comprising one or more phosphide-containing compounds.
 28. Acomposition according to any of claims 24 to 27 comprising LiFePO₄ andFe₂P, wherein at least a portion of the Fe₂P is formed in situ duringthe process comprising the step of using one or morehypophosphite-containing materials as an agent to reduce one or moremetal-containing compounds.
 29. A process for preparing a compositioncomprising a compound of the formula A_(a)M_(b)(X_(c)Y_(d))_(e)Z_(f),and one or more phosphorus-containing conductive materials, comprisingforming a mixture comprising i) one or more metal-containing precursorcompounds and optionally one or more non-metal-containing reactants andii) one or more hypophosphite-containing materials; wherein one or moreof the hypophosphite-containing materials are used as an agent to reduceone or more of the metal-containing precursor compounds; and wherein theprocess is performed in the absence of an oxidising atmosphere.
 30. Anelectrode comprising a composition according to any of claims 24 to 28.31. An energy storage device with an electrode comprising a compositionaccording to any of claims 24 to
 28. 32. An energy storage deviceaccording to claim 31 for use as one or more of a sodium ion and/orlithium ion and/or potassium ion cell; a sodium metal and/or lithiummetal and/or potassium metal ion cell; a non-aqueous electrolyte sodiumion and/or lithium ion and/or potassium ion cell; and an aqueouselectrolyte sodium ion and/or lithium ion and/or potassium ion cell. 33.A battery comprising an electrode containing a composition according toclaims 24 to 28.